The invention relates to a valve plate having a coolant duct for a compressor for generating compressed air.
The invention also relates to a method for cooling compressed air in a valve plate of a compressor, with the valve plate comprising a coolant duct.
Modern commercial vehicles, which are used in rail or road traffic, are equipped with numerous subsystems that consume compressed air. These subsystems include, for example, a service brake operated with compressed air, and an air suspension system. The supply of compressed air to the compressed air consumers is realized by means of a compressed air supply device, which includes a compressor. Ambient air is sucked in and compressed by the compressor, and before being used in the consumers, is cleaned of foreign constituents such as oil and water in further components of the compressed air supply device.
During the compression of the air in the compressor, the air is heated considerably. The heating action is increased with rising delivery pressure and rising rotational speed of the compressor. This is a disadvantage in terms of the further treatment of the compressed air, in particular the air drying. The air moisture is conventionally extracted from the air in an air filter cartridge positioned downstream of the compressor. The air filter cartridge contains a drying agent which can extract moisture from the air only up to at most 80° C. A lower maximum admissible temperature of 60° C. is therefore usually specified in order to enable effective drying. During the compression in the compressor, however, the compressed air reaches temperatures of up to 320° C. at the outlet opening of the piston chamber. At the outlet of the compressor itself, the temperatures may still be at most 220° C. This makes it necessary to cool the air between the compressor and the air filter cartridge. For this purpose, in the prior art, use is made of a pressure line of several meters in length, with it being possible for the heated compressed air to cool down as it flows through the pressure line from the compressor to the air filter cartridge, without further cooling measures. Disadvantages here are the pressure loss as a result of the long line and the structural expenditure that the pressure line itself entails.
To be able to shorten the long pressure line between the compressor and filter cartridge, it is necessary to cool the compressed air by means of active cooling. For this purpose, a so-called supercooling plate is inserted in the cylinder head of the compressor above the valve plate, which supercooling plate is traversed by a coolant and functions as a heat exchanger. By use of the supercooling plate, it is possible to lower the outlet temperature of the compressed air to 140 to 150° C. at the compressor outlet, and to shorten the adjoining pressure line by 5 to 30%. An example of a supercooling plate of this type can be found in DE 195 35 079 C2.
A disadvantage here is, in particular, the complex design resulting from the integration of the supercooling plate as a separate component into the cylinder head of the compressor, because this makes additional seals necessary.
The object on which the invention is based is that of providing a valve plate which, without a supercooling plate, provides at least the same cooling performance as a combination of a conventional valve plate and a supercooling plate.
The invention builds on the generic valve plate in that the coolant duct runs, as viewed from a piston chamber of the compressor, at least partially between the piston chamber and an air outlet valve arranged in the valve plate. As a result of this profile of the coolant duct, the entire valve plate can be cooled uniformly, with it being possible in particular for the temperature of the valve plate to be lowered in the region of the air outlet valve, which consequently increases the attainable cooling performance. The heated compressed air is therefore cooled by the coolant present in the coolant duct from the moment the compressed air reaches the air outlet valve. In particular with a viewing direction pointing perpendicularly at the valve plate from the piston chamber, it is even possible for the coolant duct to run at least partially in front of the air outlet valve.
It is expediently provided here that the coolant duct runs at least partially in a meandering fashion in a base of the valve plate. As a result of the meandering profile or course of the coolant duct in the base of the valve plate, the contact area of the coolant duct with the valve plate is increased, as a result of which greater cooling performance can be provided.
Here, it may also be provided that an air guide runs in a meandering fashion in a body of the valve plate. The meandering profile or course of the air guide also increases the attainable cooling performance since the contact surface of the medium to be cooled with the cooled valve plate is increased.
It is preferably also provided that a plurality of air outlet valves are arranged in a body of the valve plate. The simultaneous use of a plurality of air outlet valves reduces throttling losses caused by a restricted valve cross section. In this connection, the heat generation at the air outlet valves is also reduced.
The invention also relates to a compressor having a valve plate according to the invention.
The generic method is developed further in that the coolant is conducted, as viewed from a piston chamber of a compressor, at least partially between the piston chamber and an air outlet valve arranged in the valve plate. In this way, the advantages and peculiarities of the valve plate according to the invention are also implemented within the context of a method. This also applies to the particularly preferred embodiments of the method according to the invention specified below.
The method is expediently developed further in that the coolant is conducted in a meandering fashion in a base of the valve plate.
It is preferably also provided that the compressed air is conducted in a meandering fashion in a body of the valve plate.
It may also be provided that the compressed air flows into a body of the valve plate through a plurality of air outlet valves.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.